from Marc Tyrell in his comment at terraplexic

My question is this: what possible interpretation of international law allows the military of one sovereign nation to detain the citizens of another sovereign nation and charge them under a national, as opposed to an international, legal system?
First of all, this is two questions in one, which can be separated as follows:

1. What possible interpretation of international law allows one sovereign nation to charge the citizens of another sovereign nation under a national, as opposed to an international, legal system?

2. What possible interpretation of international law allows one sovereign nation to detain the citizens of another sovereign nation under a national, as opposed to an international, legal system?

Many "interpretations" allow the results. Here is a brief explanation.

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The first question hunges on jurisdiction to prescribe (legislate). The simplest case is territorial jurisdiction. I go to Canada and murder someone. Canada can legislate that anyone who murders someone while both parties are within its territory can be charged and tried in a Canadian court. Assuming I haven't fled Canada, Canada can also detain me under its territorial jurisdiction.

Marc's question goes beyond this simple case to the more complex issue of extraterritorial jurisdiction; that is where the crime involves acts or omissions outside of the nation's territory, and the criminal is located outside the nation's territory. BTW: a nation's territory is geographic; but may extend outside of its geographic territory to such things as ships, planes, space craft, diplomatic enclaves ("constructive territorial jurisdiction", "extended territorial jurisdiction", "quasi territorial jurisdiction", etc.). Assume that is not involved (let us not get into Gitmo and US foreign bases, right now).

Four bases in international law exist as justifications for exercise of extraterritorial jurisdiction to prescribe (legislate).

1. Effects-based jurisdiction. I stand in Michigan and shoot someone in Canada. Canada can legislate that as a Canadian domestic crime.

2. Protective jurisdiction. Similar to effects-based jurisdiction, this basis allows a state to criminalize conduct directed at the state from outside of the state. I sit in Michigan at my computer and direct a conspiracy to overthrow Canada's government. Canada can legislate that as a Canadian domestic crime.

3. Passive-personality jurisdiction. "Passive personality is also known as passive nationality because it refers to the nationality of the victim, while active nationality refers to the nationality of the perpetrator." I murder a Canadian national anywhere in the world because I don't like Canadians. Canada can legislate that as a Canadian domestic crime - Mexico, in fact, has done just that.

4. Universal jurisdiction. I commit a crime regarded as heinous by Canada anywhere in the world - e.g., piracy on the high seas. Canada can legislate that as a Canadian domestic crime. The German Code and others have expanded that concept into war crimes, etc.

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The second question hinges on jurisdiction to detain. That is obvious where the criminal is within the territorial jurisdiction of the detaining nation. If not, then the practical problem is how to get the criminal before the domestic court - physical control over that person.

So, we have extradition (formal), rendition (informal) and extraordinary rendition (kidnapping, in effect). The situation where a nation's military invades another nation, or occupies it (different legally from a simple invasion), provides a fourth means of obtaining custody of the criminal - if he falls into the hands of the invading army.

Now, the two questions and their answers lead to quite different results when the criminal appears before the domestic court, since question 1 goes to the subject matter jurisdiction of the court, while question 2 goes to the court's personal jurisdiction over the person charged.

If there is no subject matter jurisdiction, the case must be dismissed. So, the issues are

(1) Can Canada legislate the charge as a Canadian domestic crime (most likely, especially if under jurisdictions 1 & 2); and

(2) Has Canada legislated the charge as a Canadian domestic crime (depends on interpretation of the statute, or common law).

As to personal jurisdiction, a court may or may not dismiss even if the means of obtaining custody of the person were "extreme". Yes, persons kidnapped from foreign countries have been successfully tried. That is a messier area of the law.

The international law of jurisdiction to prescribe (legislate) is nicely summarized in this survey article:

FindArticles > Washington and Lee Law Review > Fall 2002 > Article > Print friendly
Script kiddies beware: The long arm of U.S. jurisdiction to prescribe
Eisinger, John
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This Note concludes that the effects principle allows the United States to prescribe laws against releasing viruses that substantially affect U.S. computers. [42] Furthermore, the protective principle is applicable in cases in which a computer virus specifically targets the U.S. government. [43] However, because passive personality is not as well recognized, it may provide additional justification for jurisdiction, but rarely would justify jurisdiction by itself. [44] Although universal jurisdiction enjoys wide acceptance, it does not cover computer viruses and therefore is not applicable. [45] In addition to having jurisdiction, it is reasonable for the United States to exert its jurisdiction in cases in which a virus substantially affects the United States or targets the United States government, and in which the country of the virus's origin is unable to prosecute. [46] Finally, this Note concludes that Congress intended the 1994 Act to apply extraterritorially. [47]

42. See infra notes 141-49 and accompanying text (explaining how effects principle applies to computer viruses).
43. See infra text accompanying notes 184-94 (noting how computer viruses can invoke protective principle).
44. See infra notes 220-34 and accompanying text (maintaining that passive personality is not well suited for computer viruses).
45. See infra notes 257-60 and accompanying text (concluding that computer viruses do not implicate peremptory norms and thus do not justify universal jurisdiction).
46. See infra notes 307-09 and accompanying text (determining that extraterritorial jurisdiction does not offend international comity in computer virus cases).
47. See infra notes 330-31 and accompanying text (arguing that Congress intended 18 U.S.C. [sec] 1030 (1994) to apply extraterritorially).
http://findarticles.com/p/articles/m...g=artBody;col1

What is nice about this article is that it is without the excess baggage and political spin that tend to obscure articles specifically written about detention and trial in GWOT matters.